1. Field of the Invention
This invention pertains to a liquid crystal display, and more particularly to a method of fabricating a liquid crystal display device that has improved yield.
2. Description of the Related Art
Generally, a liquid crystal display (LCD) controls the light transmissivity of liquid crystal cells arranged in a matrix pattern in response to a video signal to thereby display a picture corresponding to the video signals on a liquid crystal display panel. To this end, the LCD includes a liquid crystal display panel having liquid crystal cells arranged in an active matrix, and driving integrated circuits (IC's) drive the liquid crystal cells.
The driving IC's are usually manufactured in chip form. The driving IC's are mounted on a tape carrier package (TCP) film attached to the outer periphery of the liquid crystal panel. The driving IC's are connected by a tape automated bonding (TAB) system while being mounted along the edge of the liquid crystal panel, when they are connected by a chips on glass (COG) system. In the TAB system, the driving IC's are electrically connected to a pad portion provided at the liquid crystal panel by means of the TCP.
FIG. 1 is a plan view showing a structure of a conventional LCD device.
In FIG. 1, the LCD device has a lower plate 4 and an upper plate 6 that oppositely adhere to each other. The LCD device includes a picture display part 2 having liquid crystal cells arranged in a matrix pattern, and gate pad portions GP and data pad portions DP connected between the driving IC's and the picture display part 2.
In the picture display part 2, data lines supplied with data signals and gate lines supplied with gate signals are arranged at the lower plate 4 so as to cross each other. Each of the crossing parts is provided with a thin film transistor for switching the liquid crystal cell, and a pixel electrode connected to the thin film transistor drives the liquid crystal cell. The upper plate 6 includes coated color filters, and the color filters are separated for each cell area by black matrices. A common transparent electrode is coated on the surfaces of the color filters. Upper and lower plates 6 and 4 are spaced from each other by a spacer to provide a cell gap, which is filled with a liquid crystal material. The upper and lower plates 6 and 4 adhere to each other by means of a sealant coated on a seal 10 at the outside of the picture display part 2.
The edge area of the lower plate 4 that does not overlap with the upper plate 6 is provided with gate pad portions GP and data pad portions DP. The gate pad portion GP applies a gate signal from the gate driving IC to the gate line of the picture display part 2. The data pad portion DP applies a video signal from the data driving IC to the data line of the picture display part 2.
In the LCD device having the structure described above, a protective film for protecting the metal electrode and the thin film transistors entirely coats the lower plate 4. The pixel electrode is formed on the protective film for each cell area. The protective film is an organic protective film that enhances the aperture ratio of the pixel.
As shown in FIG. 2, a gate pad 14 of the gate pad portion GP along with a gate line of the picture display part 2 is provided on a lower substrate 1. A gate insulating film 22 and an organic protective film 24 are sequentially entirely coated on the lower substrate 1 to cover the gate pad 14. A gate contact hole 16a is formed by patterning the gate insulating film 22 and the organic protective film 24 to expose a portion of the gate pad 14. A gate protective electrode 20 is formed on the organic protective film 24 to electrically connect the gate pad 14 to the gate protective electrode 20 via the gate contact hole 16a. 
As shown in FIG. 3, a data pad 18 of the data pad part DP along with a data line of the picture display part 2 are provided on the gate insulating film 22. The organic protective film 24 entirely coats the gate insulating film 22 to cover the data pad 18. A data contact hole 16b forms by patterning the organic protective film 24 to expose a portion of the data pad 18. A data protective electrode 26 formed on the organic protective film 24 is electrically connected, via the data contact hole 16b, to the data pad 18.
The gate pad portion GP and the data pad portion DP are in contact with the TCP mounted with the driving IC by the TAB system. The gate pad 14 and the data pad 18 are electrically connected to the TCP via the gate protective electrode 20 and the data protective electrode 26 provided on the organic protective film 24. This has the goal of preventing damage to the gate pad 14 and the data pad 18 upon repetition of the TCP adhering process required for the TAB system. Also, the gate pad 14 and the data pad 18 are not exposed and hence do not react with peripheral moisture to cause their oxidative corrosion.
In order to electrically connect the TCP to the gate protective electrode 20 and the data protective electrode 26, an anisotropic conductive film 12 as shown in FIG. 4A and FIG. 4B is provided. The anisotropic conductive film 12 is coated with conductive particles 28, which form a current path between the TCP, the gate protective electrode 20 and the data protective electrode 26.
If the data pad portion DP and the gate pad portion GP adhere to the TCP mounted with the driving IC by the TAB system, then it is necessary to repeat the process of adhesive bonding and separating the TCP many times when defects caused by a misalignment occur. Accordingly, as the organic protective film 24 has a weak adhesion characteristic with respect to the gate insulating film 22, it is removed along with the TCP in the process of separating the TCP. In this case, there is a problem in that unevenness of the surface removed with the organic protective film 24 causes a weak adhesion characteristic upon re-adhering the TCP.
Furthermore, if the organic protective film 24 on the gate pad 14 and the data pad 18 is removed, then the gate protective electrode 20 and the data protective electrode 26 thereon also are removed. Accordingly, there is a problem in that the gate pad 14 and the data pad 18 are exposed to be damaged or oxidized, thereby deteriorating the characteristics of the gate pad 14 and the data pad 18.
Moreover, if a mask for eliminating the residual organic protective film 24 is used for a smooth repair process, then the productivity is reduced and hence a production time is prolonged.